Product Overview
The LXZK-0.5(0.66) open-type zero sequence current transformer is an indoor cast-resin split-core current transformer designed for cable, copper busbar, and complete switchgear earth fault protection applications. It is used for residual current detection, zero sequence current protection, and grounding fault monitoring in AC power systems with rated frequency of 50Hz or 60Hz.
The product adopts an openable / split-core structure, allowing installation around existing cables or copper busbars without disconnecting the primary conductor. This makes it suitable for retrofit projects, switchgear assembly, KHCT cabinet applications, motor feeders, generator feeders, and distribution circuits requiring fast installation and grounding protection. The secondary output can be 5A or 1A according to the connected relay or monitoring device.
Product Type
| Item | Specification |
|---|---|
| Product name | Open-Type Zero Sequence Current Transformer |
| Model series | LXZK-0.5 / LXZK-0.66 |
| Product structure | Indoor cast-resin split-core / openable zero sequence current transformer |
| Window size options | 60×35, 80×35, 100×30, 125×50, 140×30, 160×50 mm |
| Rated insulation level | 0.72/3kV |
| Rated frequency | 50Hz / 60Hz |
| Rated secondary current | 5A or 1A |
| Protection class | 10P5, 10P10, 10P15 according to selected specification |
| Installation location | Indoor |
| Typical applications | Cable earth fault protection, busbar residual current detection, zero sequence protection, KHCT switchgear metering and protection assemblies |
Product Display
Main Applications
- Indoor cable feeder earth fault protection
- KHCT complete switchgear and distribution cabinet applications
- Copper busbar residual current and zero sequence current detection
- Motor and generator feeder zero sequence overcurrent protection
- Retrofit installation where primary conductors cannot be disconnected
- Small-current grounding system protection and grounding fault alarm circuits
- Low-voltage distribution panels requiring 5A or 1A relay input signals
Key Technical Features
- Open-type split-core structure: The transformer can be opened and installed around existing cables or copper busbars, reducing installation time and avoiding conductor disassembly.
- Zero sequence current detection: Detects residual current generated by grounding faults and outputs a secondary signal for relay protection or monitoring devices.
- Cast-resin insulation: The core and secondary winding are encapsulated with resin to support insulation strength, moisture resistance, and mechanical stability.
- Multiple window sizes: Six rectangular window options are available for different busbar and cable layouts.
- 5A or 1A secondary output: Compatible with common protection relays, monitoring devices, and current input instruments.
- Protection-class performance: 10P5, 10P10, and 10P15 options are available according to current ratio and rated burden requirements.
Working Principle
The LXZK-0.5(0.66) zero sequence current transformer measures the vector sum of the currents passing through its window. In normal three-phase operation, the phase currents are balanced and the residual current is close to zero. When an insulation fault or single-phase grounding fault occurs, the current balance is broken and zero sequence current appears. The transformer converts this residual current into a 5A or 1A secondary signal for connected relays or monitoring devices.
For correct zero sequence protection, all phase conductors of the protected circuit should pass through the same transformer window in the same direction. If the transformer is used on copper busbar assemblies, the busbar group should be arranged according to the approved cabinet layout and wiring diagram.
Model Designation
The model code can be interpreted as follows:
| Code | Meaning |
|---|---|
| L | Current transformer |
| X | Zero sequence current transformer type |
| Z | Cast-resin insulated structure |
| K | Open-type / split-core structure |
| 0.5 / 0.66 | Voltage class code for indoor low-voltage systems |
| 60×35, 80×35, etc. | Window size code for busbar or cable passage |
Technical Data
| Item | Specification |
|---|---|
| Model series | LXZK-0.5 / LXZK-0.66 |
| Product type | Open-type cast-resin zero sequence current transformer |
| Rated insulation level | 0.72/3kV |
| Rated frequency | 50Hz / 60Hz |
| Rated secondary current | 5A or 1A |
| Protection class | 10P5, 10P10, 10P15 |
| Ambient temperature | -25°C to +40°C |
| Insulation structure | Cast resin insulation |
| Installation method | Split-core opening installation around cable or copper busbar |
| Applicable standards | GB 20840.1-2010, GB 20840.2-2014; project-specific requirements can be confirmed by agreement |
Window Size and Dimension Reference
| Specification | a (mm) | b (mm) | A (mm) | B (mm) | B1 (mm) | Typical Selection Use |
|---|---|---|---|---|---|---|
| 60×35 | 60 | 35 | 171 | 150 | 125 | Small cable or narrow copper busbar layout |
| 80×35 | 80 | 35 | 192 | 150 | 125 | Medium cable or busbar cabinet layout |
| 100×30 | 105 | 35 | 215 | 147 | 125 | Flat copper busbar or compact feeder layout |
| 125×50 | 130 | 50 | 245 | 168 | 147 | Larger cable group or busbar layout |
| 140×30 | 145 | 35 | 255 | 152 | 132 | Long flat busbar or narrow-height cabinet layout |
| 160×50 | 160 | 55 | 270 | 180 | 152 | Large copper busbar or cable group application |
Unit: mm. Fixed installation hole reference: 160 mm mounting hole distance and 2-15×12 long holes according to catalogue drawing. Final dimensions are subject to approved outline drawing.
Rated Current Ratio and Output Reference
| Window Specification | Protection Class | 5A Secondary Current Ratio | Rated Output Range for 5A Secondary (VA) | 1A Secondary Current Ratio | Rated Output Range for 1A Secondary (VA) |
|---|---|---|---|---|---|
| 60×35 | 10P5 / 10P10 | 50/5 to 400/5 | 1 to 10 depending on ratio and class | 50/1 to 150/1 | 1 to 3.75 depending on ratio and class |
| 80×35 | 10P5 / 10P10 | 50/5 to 400/5 | 1 to 12.5 depending on ratio and class | 50/1 to 150/1 | 1 to 5 depending on ratio and class |
| 100×30 | 10P5 / 10P10 / 10P15 | 50/5 to 400/5 | 1 to 10 depending on ratio and class | 50/1 to 150/1 | 1 to 5 depending on ratio and class |
| 125×50 | 10P5 / 10P10 / 10P15 | 50/5 to 400/5 | 1 to 15 depending on ratio and class | 50/1 to 150/1 | 1 to 5 depending on ratio and class |
| 140×30 | 10P5 / 10P10 / 10P15 | 50/5 to 400/5 | 1 to 15 depending on ratio and class | 50/1 to 150/1 | 1 to 22.5 depending on ratio and class |
| 160×50 | 10P5 / 10P10 / 10P15 | 50/5 to 400/5 | 1 to 15 depending on ratio and class | 50/1 to 150/1 | 1 to 5 depending on ratio and class |
Note: Rated output varies according to window size, current ratio, secondary current and protection class. Values beyond the catalogue table can be confirmed through technical agreement.
Service Conditions
- Installation location: indoor
- Rated insulation level: 0.72/3kV
- Rated frequency: 50Hz / 60Hz
- Ambient temperature: -25°C to +40°C
- The installation environment should be free from severe vibration, corrosive gas, conductive dust, explosive medium, and heavy pollution.
- The split-core contact surface should be clean and properly closed before operation.
- The cable, copper busbar or conductor group should pass through the window without mechanical stress on the transformer body.
- For special conductor size, cabinet layout, protection relay, or burden requirements, technical confirmation is recommended before ordering.
Standards and Compliance
The LXZK-0.5(0.66) open-type zero sequence current transformer is designed according to GB 20840.1-2010 and GB 20840.2-2014, and can also be supplied according to customer-specific project requirements. Final current ratio, rated output, protection class, routine test items, and nameplate data should be confirmed in the technical agreement.
Installation and Dimensions
The LXZK series uses an openable split-core structure. During installation, the upper and lower core sections are opened, placed around the existing cable or copper busbar group, then closed and fastened. This structure is especially suitable for retrofit projects and switchgear assemblies where the primary conductor cannot be disconnected.
Connection and Wiring Notes
- All phase conductors of the protected circuit should pass through the transformer window together in the same direction.
- For copper busbar applications, ensure that the complete protected conductor group passes through the same window.
- Do not clamp the transformer around only one phase when it is used for zero sequence protection.
- Connect secondary terminals S1 and S2 to the protection relay or monitoring device according to the wiring diagram.
- Check terminal tightening, core closing condition, relay setting and secondary wiring continuity before commissioning.
- The secondary circuit of a current transformer must not be open-circuited when the primary circuit is energized.
Installation and Safety Notes
- Confirm the model, window size, current ratio, secondary current, protection class and rated output before installation.
- Open the split-core body carefully and avoid damaging the core contact surface.
- After closing the transformer, tighten all locking bolts and confirm that the core halves are fully seated.
- Fix the transformer with the base mounting holes to prevent vibration or movement during operation.
- Check insulation clearance between the primary conductor and transformer body according to cabinet design.
- Installation and maintenance should be performed by qualified electrical personnel.
Ordering Information
Please provide the following information when ordering or requesting a quotation:
- Product model: LXZK-0.5 or LXZK-0.66
- Window specification: 60×35, 80×35, 100×30, 125×50, 140×30 or 160×50
- Rated current ratio, such as 100/5, 200/5, 300/5, 400/5, 50/1 or 100/1
- Rated secondary current: 5A or 1A
- Required protection class: 10P5, 10P10 or 10P15
- Rated output / burden in VA
- Protected conductor type: cable, copper busbar or complete switchgear busbar assembly
- Relay model, protection scheme and grounding fault detection requirement
- Quantity, drawings, certificates, inspection documents, labels or packaging requirements
Selection Guidelines
- Confirm conductor layout: Determine whether the product will be installed around cable, copper busbar, or a complete switchgear conductor group.
- Select window size: Choose 60×35, 80×35, 100×30, 125×50, 140×30 or 160×50 according to the actual conductor size and clearance.
- Confirm split-core requirement: Use LXZK when the transformer must be installed without disconnecting the existing primary conductor.
- Confirm zero sequence application: Use this product when the protection system needs residual current or grounding fault current detection.
- Select secondary current: Choose 5A or 1A according to the connected relay or monitoring device.
- Select protection class: Choose 10P5, 10P10 or 10P15 according to the protection circuit requirement.
- Check rated burden: The total burden of relays, cables and terminals should not exceed the rated output.
- Confirm installation space: Check the window size, overall dimension, mounting hole position and cabinet clearance before ordering.